Abstract: Today, the preliminary design process of power system architectures of civil aircraft is characterized by the separation into air transport association chapters. However, the complexity of an aircraft energy network and the large number of influencing design parameters and system interfaces require a common and transparent process if one is aiming at a meaningful evaluation of different system architectures with regard to overall aircraft efficiency. The variety of possible solutions requires a flexible tool that enables the system designer or aircraft architect to analyse the impact of system architecture changes at the aircraft level and the impact of aircraft level changes on system design. The outline of a simulation framework that fits these needs is presented in this paper.